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Thermofluids (Determine surface temperature)

  1. May 3, 2015 #1
    1. The problem statement, all variables and given/known data
    Air flows at a mass flow rate(m) of 0.05kg/s in a thin pipe with a diameter of 0.15m. The air enters the pipe at (Ti)103 deg celc and cools to(To) 77 deg celc after traveling 5 m in the pipe. The heat transfer coefficient between the duct outer surface and the ambient air at Tamb = 0 deg celc is ho = 6W/m2K.

    Determine the heat flux(W/m2 and the duct surface temperature at x = 5m. The duct wall is thin and conduction effect can be neglected.

    2. Relevant equations
    q''[W/m2] .....Might need this equation ??

    3. The attempt at a solution

    q [W] = mcp(Ti-To) = 1313 W where cp = 1010 J/KgK for air flowing through pipe.

    If I'm not told that the surface heat flux is constant can I still apply the equation above? Also, without knowing surface conditions such as constant surface heat flux or constant surface temperature is this problem solvable?
  2. jcsd
  3. May 3, 2015 #2
    Have you learned how to determine the heat transfer coefficient for the internal flow? If so, please tell us how you would proceed.

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